Ellipsometry is a well known means by which to non-destructively monitor material systems, (samples). In brief, a polarized beam of electromagnetic radiation of one or more wavelengths is caused to impinge upon a material system, (sample), along one or more angles of incidence and interact with said material system, (sample). Beams of electromagnetic radiation can be considered as comprised of two orthogonal components, (ie. “P” and “S”), where “P” identifies a plane which contains both an incident beam of electromagnetic radiation, and a normal to an investigated surface of a material system, (sample), being investigated, and where “S” identifies a plane perpendicular to the “P” plane and parallel to said surface of said material system, (sample). A change in polarization state in a polarized beam of electromagnetic radiation caused by interaction with a material system, (sample), is representative of properties of said material system, (sample). (Note, while an incomplete characterization, Polarization State basically refers to a magnitude of a ratio of orthogonal component magnitudes in a polarized beam of electromagnetic radiation, and a phase angle therebetween). Generally two well known angles, (PSI and DELTA), which characterize a material system, (sample), at a given Angle-of-Incidence, are determined by analysis of data and represent change in polarization state. Additional sample identifying information is often also obtained by application of ellipsometry, including layer thicknesses, (including thicknesses for multilayers), optical thicknesses, sample temperature, refractive indicies and extinction coefficients, index grading, sample composition, surface roughness, alloy and/or void fraction, parameter dispersal and spectral dependencies on wavelength, vertical and lateral inhomogenieties etc.
Continuing, Ellipsometer Systems generally include a source of a beam of electromagnetic radiation, a Polarizer means, which serves to impose a linear state of polarization on a beam of electromagnetic radiation, a Stage for supporting a material system, (sample), and an Analyzer means which serves to select a polarization state in a beam of electromagnetic radiation after it has interacted with a material system, (sample), and pass it to a Detector System for analysis therein. As well, one or more Compensator(s) can be present and serve to affect a phase angle change between orthogonal components of a polarized beam of electromagnetic radiation. A number of types of ellipsometer systems exist, such as those which include rotating elements and those which include modulation elements. Those including rotating elements include Rotating Polarizer (RP), Rotating Analyzer (RA) and Rotating Compensator (RC). The presently disclosed invention can comprise a Rotating Compensator Ellipsometer System. It is noted that Rotating Compensator Ellipsometer Systems do not demonstrate “Dead-Spots” where obtaining data is difficult. They can read PSI and DELTA of a Material System over a full Range of Degrees with the only limitation being that if PSI becomes essentially zero (0.0), one can't then determine DELTA as there is not sufficient PSI Polar Vector Length to form the angle between the PSI Vector and an “X” axis. In comparison, Rotating Analyzer and Rotating Polarizer Ellipsometers have “Dead Spots” at DELTA's near 0.0 or 180 Degrees and Modulation Element Ellipsometers also have “Dead Spots” at PSI near 45 Degrees. The utility of Rotating Compensator Ellipsometer Systems should then be apparent. Another benefit provided by fixed Polarizer (P) and Analyzer (A) positions is that polarization state sensitivity to input and output optics during data acquisition is essentially non-existent. This enables relatively easy use of optic fibers, mirrors, lenses etc. for input/output.
Known relevant patents include a patent to Johs et al., U.S. Pat. No. 5,872,630, from which the present application is derived as a CIP via intervening CIP applications. Said 630 patent describes:                A spectroscopic rotating compensator material system investigation system comprising a source of a polychromatic beam of electromagnetic radiation, a polarizer, a stage for supporting a material system, an analyzer, a dispersive optics and at least one detector system which contains a multiplicity of detector elements, said spectroscopic rotating compensator material system investigation system further comprising at least one compensator(s) positioned at a location selected from the group consisting of:                    before said stage for supporting a material system;            after said stage for supporting a material system; and            both before and after said stage for supporting a material system;                        such that when said spectroscopic rotating compensator material system investigation system is used to investigate a material system present on said stage for supporting a material system, said analyzer and polarizer are maintained essentially fixed in position and at least one of said at least one compensator(s) is caused to continuously rotate while a polychromatic beam of electromagnetic radiation produced by said source of a polychromatic beam of electromagnetic radiation is caused to pass through said polarizer and said compensator(s), said polychromatic beam of electromagnetic radiation being also caused to interact with said material system, pass through said analyzer and interact with said dispersive optics such that a multiplicity of essentially single wavelengths are caused to simultaneously enter a corresponding multiplicity of detector elements in said at least one detector system.Said 630 patent also, amongst other disclosure, describes a Mathematical Regression based Calibration procedure which makes possible the use of essentially any compensator regardless of non-achromatic characteristics.        
Another patent to Johs, from which the 630 patent was Continued-in-Part, is No. 5,666,201, filed Sep. 20, 1995. The focus in said 201 patent comprises a detector arrangement in which multiple orders of a dispersed beam of electromagnetic radiation are intercepted by multiple detector systems. However, Claim 8 in the 201 patent, in combination with a viewing the Drawings therein, provide conception of the Spectroscopic Rotating Compensator Ellipsometer, as Claimed in Claim 1 of the JAW 630 patent and, in fact, the 630 patent issued in view of a Terminal Disclaimer based upon the 201 patent. A CIP of the 630 patent, is U.S. Pat. No. 6,353,477 to Johs et al. which describes preferred multiple element compensators.
It is known to generate polychromatic electromagnetic radiation by establishing a plasma, such as an inductively coupled plasma. It is also known to apply such plasma generated polychromatic electromagnetic radiation in polychromatic investigation of samples. For instance, it is known to inject particulate samples into plasmas and monitor an emitted wavelength spectrum to identify the chemical composition thereof. Recently, 31 Oct. 2003 a Japanese Abstract 2003-307491 was published, based upon Japanese Application 2003-048215, filed 21 Jan. 2003. Said Abstract discloses a system for and use of plasma generated polychromatic electromagnetic radiation to provide a beam which is directed through apertures and lenses to impinge upon a sample. After the resulting interaction with said sample, said polychromatic electromagnetic radiation is applied to characterize said sample. Application is in a Spectrometer system.
A patent to Zhu et al., U.S. Pat. No. 5,259,254 is disclosed to show that it is known to apply Inductively Coupled Plasma (ICP) in exciting Analytes. Patent to Chen et al., U.S. Pat. No. 5,233,156, is disclosed to show that (ICP) Torches are known. And, U.S. Pat. No. 5,192,865 to Zhu is disclosed to show that it is known to excite atoms into a Metastable state using an (ICP) system, followed by injecting Analyte into a multiplicity of said excited atoms, and direct the result through a skimmer and into a Mass Spectrometer. The invention in the Japanese Application 2003-048215 performs a similar function, with the beam of excited atoms being directed through a Skimmer in a Mass Spectrometer-like apparatus, and further provides a lens after said Skimmer which focuses electromagnetic radiation emitted from said Metastable Atoms. The Japanese 215 Application also shows that the beam of excited atoms is directed through said skimmer at an angle so as not to impact the lens, which lens is positioned such that were the Metastable atoms not entered at said angle, they would impinge thereupon.
Another patent, U.S. Pat. No. 5,382,804 to D′Silva describes photoionization lamp sources constructed from machinable photon radiation transparent material, such as crystalline magnesium or lithium fluoride which pass wavelengths emitted by excited Argon, Krypton and Xenon at 11.8, 10.2 and 9.5 eV respectively. This can be further described as low pressure discharge Argon provides an emitted wavelength of 104.8 NM, Xenon at 146.5 NM and Kyrpton at 123.5 NM. And of course, combinations of gasses can be utilized.
Another patent which describes a system for providing an output beam of polychromatic electromagnetic radiation which has a relatively broad and flattened intensity vs. wavelength characteristic over a wavelength spectrum is U.S. Pat. No. 6,268,917. Said patent describes a system comprising at least a first and a second source of polychromatic electromagnetic radiation and at least a first electromagnetic beam combining means. Said at least a first electromagnetic beam combining means is positioned with respect to said first and second sources of polychromatic electromagnetic radiation such that a beam of polychromatic electromagnetic radiation from said first source of polychromatic electromagnetic radiation passes through said at least a first electromagnetic beam combining means, and such that a beam of polychromatic electromagnetic radiation from said second source of polychromatic electromagnetic radiation reflects from said at least a first electromagnetic beam combining means and is comingled with said beam of polychromatic electromagnetic radiation from said first source of polychromatic electromagnetic radiation which passes through said at least a first electromagnetic beam combining means. Said resultant beam of polychromatic electromagnetic radiation substantially is said output beam of polychromatic electromagnetic radiation which has a relatively broad and flattened intensity vs. wavelength over a wavelength spectrum, comprising said comingled composite of a plurality of input beams of polychromatic electromagnetic radiation which individually do not provide such a relatively broad and flattened intensity vs. wavelength over a wavelength spectrum characteristic.
It is further known to develop high temperature plasmas, which emit an essentially Black Body Spectrum, in magnetically contained small volumes which appear as point sources some distance therefrom, when viewed axially.
Benefit results from the application of custom wavelength content electromagnetic radiation in ellipsometer or the like systems. In particular, a plasma can be customized as regards its wavelength emission via the inclusion of selected analytes in a gas, (eg. argon), in which it is formed, and by selection of the carrier gas.
It is also generally known that many sources of electromagnetic radiation which provide wavelengths down to and below 193 nm typically provide said wavelengths at a lower intensity than is associated with longer, (eg. visible range), wavelengths. Further, it is known that optical elements through which electromagnetic radiation is caused to pass often have different effects on different wavelengths, (ie. dispersal occurs), with a result being that electromagnetic radiation of one wavelength proceeds along a different path than does electromagnetic radiation of a different wavelength. Where said electromagnetic radiation is to be focused onto a spot on a sample said dispersion leads to the spot being of a diameter greater than 35 micron. In that light, it is disclosed that it is also known to place a lens in the path of a beam of electromagnetic radiation to, for instance, focus or collimate it. It is further known that single element lenses have different refractive effects on different wavelengths. Multiple element lenses, wherein at least two elements are present and are made of different materials, are known to more achromatic and uniformly refract different wavelengths. A consideration in constructing previously known multiple element lenses involves physical interconnection between elements. Rigid elements must be shaped to sequentially fit one element to the next. It would be of benefit if a generic system could be provided which could be tailored to have desired achromatic effects on multiple wavelengths without modifying rigid components.
It is also known in the art to focus a broadband beam of electromagnetic radiation onto a small spot in ellipsometers by reflective, as well as refractive optics. Typically, said prior art systems image a small aperture onto a spot on a sample with high demagnification, and, particularly where refractive optics are used, suffer from varying degrees of optical aberrations, (eg. spherical, chromatic, astigmatism etc.). In addition, surfaces of mirrors can be non-ideal as a result of non-traditional manufacturing of special optics, and the cost of non-spherical optics is high. It is also known that spherical optics can be fashioned to image an object with 1:1 magnification with essentially no aberrations. Such a 1:1 imager is, for instance, disclosed in an expired U.S. Pat. No. 3,748,015 which describes an imaging system comprising two elements:                a) a concave spherical mirror; and        c) a convex spherical mirror;said elements being arrange such that electromagnetic radiation caused to approach the concave spherical reflects at a first location thereon is reflected to said a convex spherical mirror, from which it reflects onto a second location of said concave spherical mirror, from which it reflects as a beam of electromagnetic radiation, which, if the electromagnetic radiation caused to approach the concave spherical mirror at a first location was, for instance, an imaged aperture, appears as a small spot on the sample. It is emphasized that a colliminated electromagnetic beam is not “focused” by the 1:1 imager, but rather a substantially point source is imaged thereby.        
Other patents, U.S. Pat. No. 5,859,424 to Norton and U.S. Pat. No. 5,608,526 to Piwonka-Corle et al., are of interest as they describe focusing a collimated beam using a curved reflective mirror. This, it is noted, is in contrast to imaging a point source onto, for instance, a sample, as the 1:1 imaging system described in Expired U.S. Pat. No. 3,748,015 can be applied to accomplish in an ellipsometer system, (emphasis added).
A patent to Gilby, U.S. Pat. No. 4,175,864 is disclosed as it describes use of spherical and flat mirrors to focus a light slit.
The disclosed invention provides sources of electromagnetic radiation which provide desired wavelength output; means for improving relative intensity of electromagnetic radiation emitted by a source at wavelengths in, for instance, IR ad UV ranges; means for directing electromagnetic radiation emitted by a source along a desired locus; and reflective imaging and refractive focusing means for achromatically providing a small spot size of electromagnetic radiation where it is caused to impinge upon a sample surface.